SIDE EFFECTS

In patients taking DAYPRO ALTA (oxaprozin potassium tablets), oxaprozin, or
other NSAIDs , the following are the most frequently reported adverse experiences
occurring in approximately 1-10% of patients (see CLINICAL
STUDIES, Osteoarthritis):

DRUG INTERACTIONS

Aspirin

When DAYPRO ALTA (oxaprozin) is administered with aspirin, its protein binding is reduced, although the clearance of free DAYPRO ALTA (oxaprozin) is not altered. The clinical significance of this interaction is not known; however, as with other NSAIDs, concomitant administration of oxaprozin potassium and aspirin is not generally recommended because of the potential of increased adverse effects.

Methotrexate

NSAIDs have been reported to competitively inhibit methotrexate accumulation in rabbit kidney slices. This may indicate that they could enhance the toxicity of methotrexate. Caution should be used when NSAIDs are administered concomitantly with methotrexate.

Coadministration of oxaprozin with methotrexate results in approximately a
36% decrease in oral plasma clearance of methotrexate. A reduction in methotrexate
dosage may be considered due to the potential for increased methotrexate toxicity
associated with the increased exposure.

ACE-Inhibitors

Reports suggest that NSAIDs may diminish the antihypertensive effect of ACE-
inhibitors. This interaction should be given consideration in patients taking
NSAIDs concomitantly with ACE-inhibitors. Oxaprozin has been shown to alter
the pharmacokinetics of enalapril (significant decrease in dose-adjusted AUC0-24hr
and Cmax) and its active metabolite enalaprilat (significant increase in dose-adjusted
AUC0-24).

Diuretics

Clinical studies, as well as post-marketing observations, have shown that DAYPRO
ALTA can reduce the natriuretic effect of furosemide and thiazides in some patients.
This response has been attributed to inhibition of renal prostaglandinsynthesis.
During concomitant therapy with NSAIDS patients should be observed closely for
signs of renal failure (see WARNINGS, Renal Effects),
as well as to assure diuretic efficacy.

Lithium

DAYPRO ALTA (oxaprozin) , like other NSAIDs, has produced an elevation of plasma lithium levels and a reduction in renal lithium clearance. The mean minimum lithium concentration was increased 15% and the renal clearance was decreased by approximately 20%. These effects have been attributed to inhibition of renal prostaglandin synthesis by NSAIDs. Thus, when NSAIDs and lithium are administered concurrently, lithium level should be monitored and subjects should be observed carefully for signs of lithium toxicity.

Warfarin

The effects of warfarin and NSAIDs on GI bleeding are synergistic, such that users of both drugs together have a risk of serious GI bleeding higher than the users of either drug alone.

Glyburide

While oxaprozin does alter the pharmacokinetics of glyburide, coadministration of oxaprozin to type II non-insulin dependent diabetic patients did not affect the area under the glucose concentration curve or the magnitude or duration of control. However, it is advisable to monitor patients' blood glucose in the beginning phase of glyburide and oxaprozin co-therapy.

H2— receptor antagonists

The total body clearance of oxaprozin was reduced by 20% in subjects who concurrently received therapeutic doses of cimetidine or ranitidine; no other pharmacokinetic parameter was affected. A change of clearance of this magnitude lies within the range of normal variation and is unlikely to produce a clinically detectable difference in the outcome of therapy.

Laboratory Test Interactions:

False-positive urine immunoassay screening tests for benzodiazepines have been
reported in patients taking oxaprozin. This is due to lack of specificity of
the screening tests. False-positive test results maybe expected for several
days following discontinuation of oxaprozin therapy. Confirmatory tests, such
as gas chromatography/mass spectrometry, will distinguish oxaprozin from benzodiazepines.

Last reviewed on RxList: 4/17/2008
This monograph has been modified to include the generic and brand name in many instances.